Field of the Invention
The invention relates to a rigid flex circuit board, and more particularly, to a rigid flex circuit board capable of improving thermal shock reliability.
Description of Related Art
Based on the flexibility of the insulating layer, the circuit board can be divided into a rigid circuit board and a flexible circuit board. When electronic components are soldered to the flexible circuit board, the flexible circuit board cannot provide sufficient structural strength. Moreover, when electronic components are soldered, although the rigid circuit board provides better structural strength, the flexibility thereof is poor, and therefore the application of the rigid circuit board is limited.
The rigid flex circuit board is a combination of a flexible circuit board and a rigid circuit board, and has both the flexibility of the flexible circuit board and the structural strength of the rigid circuit board. When the rigid flex circuit board is manufactured via conventional process, to achieve the characteristics of the bent region of a flex sheet, a bonding sheet is generally used to laminate the entire sheet surface. However, after repeated lamination process, the process conditions of high temperature and high pressure may cause layering to the flex sheet between the bonding sheets, or risk of compromised reliability during thermal shock test. Moreover, in the design of a multi-layer flex sheet, if copper layers of the flex sheet layer are disposed facing each other, then short circuit may occur, and therefore the design limit that copper layers cannot be stacked facing each other exists, such that the cost of the flex sheet material is increased.
Based on the above, how to solve the issue of compromised reliability of the multi-layer flex sheet in thermal shock testing and overcome the design limitation that copper layers cannot be disposed facing each other at the same time is an important object for those skilled in the art.